Scorpio faces Taurus in the Zodiac wheel, so this is it's polar opposite.
Taurus is about the practical, material world and is almost shallow and superficial.
Scorpio, on the other hand, is deep and dark, secretive and tries to find out what something really is about, instead of just taking things as they are presented (like a Taurus).
Taurus is about a safe home, good food and all the things that serve a physical well being.
Scorpio seeks emotional well-being and security. That's why they fear vulnerability, losing power or their secrets being exposed.
Taurus is about the things you have, Scorpio is about the wisdom and power you have - the things you cannot perceive with your senses. Taurus, however, is a really sensual sign - they love nice tastes, sounds, touches...
Scorpio, then, is about the non-mundane, hidden world.
Libra is the sign of the scales, equality, combining opposites and creating harmony.
Scorpio is the sign of extremes, of obsession and compulsion, holding onto people and ideas and even paranoia.
Libra is also the sign of giving to others, while Scorpio is the sign of other people's rescources. They are often associated with "vampirism" - sucking out other people's life energy.
Sagittarius is about religion, faith, idealism and all things holy while Scorpio is about dark magic, the occult, alchemy and power.
Sagittarius is about morals and wanting to have that halo over everything they are and everything they do, they want to be the morally good guru or priest.
Scorpio, though, is the mystical, dark shaman who will break rules and explore taboos.